Optically controlled terahertz metasurface modulator with ultra-high Q value

Abstract

This invention discloses a light-controlled terahertz metasurface modulator with ultra-high Q-value, comprising a transmission substrate layer and a frequency control structure; the frequency control structure is stacked on the upper surface of the transmission substrate layer; the frequency control structure includes a surface periodic structure; the surface periodic structure is composed of multiple transmission units arranged in a regular matrix. This invention controls the application of laser pulses to the photosensitive material layer of the modulator by controlling an external laser, causing it to generate a large number of photo-excited free carriers, forming a periodic unit resonator, thereby achieving the modulation of the Q-value of the transmitted terahertz wave within a specific frequency band. Compared with existing technologies, this invention can achieve and control an ultra-high quality factor within an ultra-narrow frequency range, is suitable for various applications, has a simple structure, and is easy to operate.

Description

Technical Field

[0001] This invention relates to the fields of terahertz modulation devices and wireless communication, and particularly to a light-controlled terahertz metasurface modulator with ultra-high Q value. Background Technology

[0002] Recently, with the rapid development of network communication technology, 5G communication technology has matured and gradually become commercialized. Globally, fundamental theoretical research on 6G communication technology, which offers wider spectrum and faster transmission speeds, has begun. Terahertz communication technology is expected to achieve data transmission speeds up to 1 Tbit / s and is anticipated to become the main operating frequency band for 6G communication, representing one of the best solutions for realizing 6G communication technology.

[0003] Terahertz ultra-high Q modulators are a key fundamental component in terahertz communication technology. Their ultra-high Q value enables rapid modulation in the terahertz band, supporting higher data transmission rates. This is crucial for terahertz communication systems, especially for future wireless communication and data exchange technologies.

[0004] Currently, terahertz modulators mainly utilize metal composite tunable materials to design resonant structures and achieve amplitude control through electronic or thermal modulation. However, terahertz modulators using electronic modulation require a power source directly connected to the modulator, while those using thermal modulation require the heating source to be close to the modulator. These limitations restrict the application scenarios of the modulators to some extent. Summary of the Invention

[0005] The purpose of this invention is to solve the problems in the background art by proposing a light-controlled terahertz metasurface modulator with ultra-high Q value.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A light-controlled terahertz metasurface modulator with ultra-high Q value includes a transmission substrate layer and a frequency control structure; the frequency control structure is stacked on the upper surface of the transmission substrate layer.

[0008] The frequency control structure includes a surface periodic structure;

[0009] The surface periodic structure is composed of multiple transmission units arranged in a regular matrix;

[0010] Each of the aforementioned transmission units is composed of two silica patches and a light-modulating material patch (22), wherein the two silica patches are a left silica patch and a right silica patch;

[0011] The left-side silica patch is a fan-shaped piece made of silica material, and the right-side silica patch is a fan-shaped piece made of silica material;

[0012] The left and right silica patches are identical in shape and equal in size.

[0013] The left and right silica patches are located on opposite sides, and there is a gap between the left and right silica patches.

[0014] The two light-modulating material patches are the left light-modulating material patch and the right light-modulating material patch, respectively;

[0015] The left-side light-modulating material patch is a fan-shaped material made of light-modulating material, and the right-side light-modulating material patch is a fan-shaped material made of light-modulating material;

[0016] The left and right light-controlling material patches are identical in shape and equal in size.

[0017] The left and right light-modulating material patches are located on opposite sides, and there is a gap between the left and right light-modulating material patches.

[0018] The radii of the left and right silica patches are equal to those of the left and right light-modulating material patches.

[0019] The upper straight edge of the left silica patch is connected to the lower straight edge of the left light-modulating material patch;

[0020] The upper straight edge of the right-side silica patch is connected to the lower straight edge of the right-side light-modulating material patch;

[0021] The central angles of the left-side silica patch and the left-side light-modulating material patch are complementary;

[0022] The central angles of the right-side silica patch and the right-side light-modulating material patch are complementary.

[0023] Preferably, each of the transmission units is symmetrical about its longitudinal central axis.

[0024] Preferably, the transmission substrate layer is made of terahertz high-transmittance materials such as high-resistivity silicon, mica substrate, and sapphire substrate;

[0025] The silica patch is made of terahertz high-transmittance materials such as high-resistivity silicon, silicon nitride, and polyimide.

[0026] The light-modulating material patch is made of terahertz photosensitive materials such as photosensitive silicon, transition metal sulfides, and vanadium dioxide.

[0027] Preferably, the area covered by the surface periodic structure is larger than the area of ​​the terahertz beam spot illuminating the modulator body.

[0028] Preferably, the area covered by the surface periodic structure is 1.5 to 2.5 times the area of ​​the terahertz beam spot illuminating the modulator body.

[0029] Preferably, the laser spot area is greater than or equal to the coverage area of ​​all periodic transmission units of the frequency control structure.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] This invention utilizes silica to design a terahertz metasurface with C2 symmetry. Under C2 symmetry, the structural symmetry ensures the symmetrical propagation characteristics of terahertz waves in different directions, suppressing coupling with radiation modes. When the metasurface structure possesses C2 symmetry, the radiation channel of the resonant mode is closed, preventing the structure from effectively radiating energy and forming a bound state. In this state, the local electromagnetic field on the metasurface can be precisely controlled and localized, preventing energy escape through external radiation channels, resulting in no energy loss in the resonant state and an infinite Q-value in the transmission curve. When vanadium dioxide phase change material is added to the metasurface, the original C2 symmetry is disrupted, transforming the continuous bound state mode into a quasi-continuous bound state mode. The high Q-value primarily stems from the low radiation loss in the quasi-continuous bound state mode. In the quasi-continuous bound state mode, the resonant mode of the metasurface produces almost no radiation, allowing energy to remain within the resonant cavity for an extended period. This ultra-long energy residence time leads to an ultra-high Q-value. Attached Figure Description

[0032] Figure 1 A schematic diagram of the three-dimensional structure of a light-controlled terahertz metasurface modulator with ultra-high Q value;

[0033] Figure 2 A top view of a light-controlled terahertz metasurface modulator with ultra-high Q value;

[0034] Figure 3 This is a schematic diagram of the structure of a transmission unit;

[0035] Figure 4 This is a schematic diagram of the terahertz wave transmittance curves under the conditions of no pump light excitation and pump light excitation according to the present invention.

[0036] In the figure: 1 Transmission substrate; 2 Frequency control structure; 21 Silicon dioxide patch; 22 Vanadium dioxide patch. Detailed Implementation

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0038] See Figure 1 A light-controlled terahertz metasurface modulator with ultra-high Q value includes a modulator body, which is composed of a transmission substrate layer 1 and a frequency control structure 2. The transmission substrate layer 1 can be a terahertz high-transmittance material such as high-resistivity silicon, mica, or sapphire. The shape of the transmission substrate layer 1 can be circular, square, or polygonal, as long as it can accommodate the frequency control structure 2. In a preferred embodiment of the invention, the transmission substrate layer 1 is rectangular, and the thickness of the transmission substrate layer is 10 μm. The frequency control structure 2 is stacked on the upper surface of the transmission substrate layer 1.

[0039] See Figure 2 The frequency control structure 2 includes a surface periodic structure.

[0040] The surface periodic structure is located in the middle of the frequency control structure 2 and consists of multiple transmission units arranged in a regular matrix. Each transmission unit is as follows: Figure 3 As shown, the entire structure is symmetrical about its longitudinal central axis. Each transmission unit consists of two silicon dioxide patches 21 and a light-modulating material patch 22. In a preferred embodiment of the invention, the thickness of the silicon dioxide patches 21 is 1–4 μm, and the thickness of the light-modulating material patch 22 is 0.2–4 μm. The silicon dioxide patches can be high-resistivity terahertz wave high-transmittance materials such as high-resistivity silicon, silicon nitride, and polyimide; the light-modulating material patches can be photosensitive materials such as photosensitive silicon, transition metal sulfides, and vanadium dioxide.

[0041] Two silica patches 21 are designated as a left silica patch 21 and a right silica patch 21. Both the left and right silica patches 21 are fan-shaped and made of the same terahertz wave high-transmittance material such as high-resistivity silicon, silicon nitride, or polyimide. The left and right silica patches 21 are identical in shape and size; they are located on opposite sides with a gap between them. In a preferred embodiment of the invention, the central angle of the silica patch 21 is 60°–87°.

[0042] The two light-modulating material patches 22 are designated as the left and right light-modulating material patches 22, respectively. Both the left and right light-modulating material patches 22 are identical fan-shaped and made of materials such as photosensitive silicon, transition metal sulfides, and vanadium dioxide. The left and right light-modulating material patches 22 are identical in shape and size. They are located on opposite sides, with a gap between them.

[0043] The radii of the left and right silicon dioxide patches 21, the left and right light-modulating material patches 22, and the right light-modulating material patches 22 are equal. The upper straight edge of the left silicon dioxide patch 21 is connected to the lower straight edge of the left light-modulating material patch 22. The upper straight edge of the right silicon dioxide patch 21 is connected to the lower straight edge of the right light-modulating material patch 22. The central angles of the left silicon dioxide patch 21 and the left light-modulating material patch 22 are complementary. The central angles of the right silicon dioxide patch 21 and the right light-modulating material patch 22 are complementary.

[0044] In operation, the terahertz wave is incident directly above the modulator, i.e., directly above the surface periodic structure. It then passes through the frequency control layer and is transmitted through the lower surface of the transmission substrate. To ensure unobstructed passage of the terahertz beam from the modulator, the area covered by the surface periodic structure (i.e., all transmission units) is larger than the area of ​​the terahertz beam spot illuminating the modulator, being 1.5 to 2.5 times the area of ​​the terahertz beam spot. The terahertz wave is incident perpendicularly from the upper surface of the frequency control layer. To ensure the excitation (pumping) effect of the laser on the modulator, the laser spot area is greater than or equal to the coverage area of ​​all periodic transmission units in the frequency control layer. In this invention, the laser spot area is 2 to 3 times the coverage area of ​​all periodic transmission units in the frequency control layer, and the laser pumps obliquely from the upper surface of the frequency control layer. The laser used in this invention has a wavelength of 800 nm to 1064 nm and a power of 0.5 W to 1.5 W.

[0045] This invention has the following two operating states:

[0046] The first working state: When there is no laser pump on the upper surface of the frequency control layer, the optical modulation material in the frequency control layer will not undergo photoelectric effect and will not generate photoexcited carriers. The optical modulation material is in a non-metallic state. At this time, the silicon dioxide material and the non-metallic optical modulation material together form a quasi-continuum bound state mode. Its resonance mode hardly produces radiation. The energy stays in the resonant cavity for a long time, and the ultra-long energy residence time produces an ultra-high Q value. Figure 4 This is a schematic diagram of the terahertz wave transmittance curves under conditions of no pump light excitation and pump light excitation, based on the present invention. Figure 4It can be seen that within the ultra-narrow frequency band of 701.625GHz to 702.125GHz, the terahertz wave transmittance is 46%, and the transmission curve quality factor Q is 2314.75.

[0047] The second operating state: When laser pumping occurs on the upper surface of the frequency control layer, the optical modulation material of the frequency control layer will undergo the photoelectric effect, generating photoexcited charge carriers. The optical modulation material transitions to a metallic state. At this time, the silicon dioxide material and the metallic optical modulation material together form a quasi-continuum bound state mode. Its resonant mode is enhanced compared to when the optical modulation material is in a non-metallic state, resulting in decreased terahertz wave transmittance and increased Q value. See also... Figure 4 Within the ultra-narrow frequency band of 701.625 GHz to 702.125 GHz, the terahertz wave transmittance is 38%, and the transmission curve quality factor Q value is 3588.02.

[0048] The quality factor of the transmitted terahertz wave can be modulated by changing the laser power pumped onto the surface of the frequency control layer. Figure 4 It can be seen that within the ultra-narrow frequency band of 701.625 GHz to 702.125 GHz, the transmitted terahertz wave can achieve a quality factor Q value that varies within the range of 2314.75 to 3588.02.

[0049] This invention controls the application of laser pulses to the photosensitive material layer of a modulator using an external laser, generating a large number of photoexcited free carriers to form a periodic unit resonator. This allows for the modulation of the Q-factor of transmitted terahertz waves within a specific frequency band. Compared to existing technologies, this invention achieves and modulates an ultra-narrow frequency range, is suitable for various applications, and features a simple structure and convenient operation.

[0050] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A light-controlled terahertz metasurface modulator with ultra-high Q value, characterized in that, It includes a transmission substrate layer (1) and a frequency control structure (2); the frequency control structure (2) is stacked on the upper surface of the transmission substrate layer (1); The frequency control structure (2) includes a surface periodic structure; The surface periodic structure is composed of multiple transmission units arranged in a regular matrix; Each of the aforementioned transmission units consists of two silica patches (21) and a light-modulating material patch (22), wherein the two silica patches (21) are a left silica patch (21) and a right silica patch (21); The left silicon dioxide patch (21) is a fan-shaped material made of silicon dioxide, and the right silicon dioxide patch (21) is a fan-shaped material made of silicon dioxide. The left and right silica patches (21) are identical in shape and size. The left silicon dioxide patch (21) and the right silicon dioxide patch (21) are located on opposite sides, and there is a gap between the left silicon dioxide patch (21) and the right silicon dioxide patch (21); The two light-modulating material patches (22) are the left light-modulating material patch (22) and the right light-modulating material patch (22); The left-side light-modulating material patch (22) is a fan-shaped material made of light-modulating material, and the right-side light-modulating material patch (22) is a fan-shaped material made of light-modulating material; The left-side light-modulating material patch (22) and the right-side light-modulating material patch (22) have the same shape and are equal in size; The left light-modulating material patch (22) and the right light-modulating material patch (22) are located on opposite sides, and there is a gap between the left light-modulating material patch (22) and the right light-modulating material patch (22); The radii of the left silicon dioxide patch (21) and the right silicon dioxide patch (21) are equal to those of the left light-modulating material patch (22) and the right light-modulating material patch (22); The upper straight edge of the left silica patch (21) is connected to the lower straight edge of the left light-modulating material patch (22); The upper straight edge of the right-side silica patch (21) is connected to the lower straight edge of the right-side light-modulating material patch (22); The central angles of the left-side silica patch (21) and the left-side light-modulating material patch (22) are complementary; The central angles of the right-side silica patch (21) and the right-side light-modulating material patch (22) are complementary.

2. The optically controlled terahertz metasurface modulator with ultra-high Q value according to claim 1, characterized in that: Each of the aforementioned transmission units is symmetrical about its longitudinal central axis.

3. The optically controlled terahertz metasurface modulator with ultra-high Q value according to claim 1, characterized in that: The transmission substrate layer (1) is made of a high-resistivity silicon, mica substrate and sapphire substrate terahertz high-transmittance material; The silica patch (21) is made of terahertz high transmittance materials such as high-resistivity silicon, silicon nitride, and polyimide; The light-modulating material patch (22) is made of terahertz photosensitive materials such as photosensitive silicon, transition metal sulfides and vanadium dioxide.

4. A light-controlled terahertz metasurface modulator with ultra-high Q value according to claim 1, characterized in that: The area covered by the surface periodic structure is larger than the area of ​​the terahertz beam spot illuminating the modulator body.

5. A light-controlled terahertz metasurface modulator with ultra-high Q value according to claim 2, characterized in that: The area covered by the surface periodic structure is 1.5 to 2.5 times the area of ​​the terahertz beam spot illuminating the modulator body.

6. A light-controlled terahertz metasurface modulator with ultra-high Q value according to claim 4, characterized in that: When a laser is pumped onto the upper surface of the frequency control layer, the laser spot area is greater than or equal to the coverage area of ​​all periodic transmission units of the frequency control structure.

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